The present invention relates to implantable medical devices for delivering a liquid therapeutic substance to a delivery site within a patient. More particularly, it relates to systems and methods for selectively blocking the catheter access port of an implantable therapeutic substance delivery device.
A variety of implantable medical devices are available for treating patients. For example, implantable therapeutic substance delivery devices are typically used to deliver infusion media or therapeutic substances (such as medication) to a patient at a regulated dosage. The implantable therapeutic substance delivery device (sometimes referred to as a drug pump or medicament pump) is implanted by a clinician into a patient at a location appropriate for the therapy. Typically, an infusion catheter is connected to a discharge outlet of the device, and is implanted/positioned to infuse the therapeutic substance at the desired therapy site so as to treat a condition such as pain, spasticity, cancer, neurodegenerative disease, trauma, etc. The term “implantable therapeutic substance delivery device” as used herein, refers to any device for delivering medicaments including, but not limited to, bladder pumps, accumulator pumps, fixed-rate bellows pumps, and the like.
In general terms, the implantable therapeutic substance delivery device commonly includes a drug reservoir containing a volume of the infusion media, along with a pumping mechanism to propel the infusion media in some metered or constant flow dosage to the desired delivery site from the reservoir via the catheter. Over time, the reservoir becomes depleted and it is necessary to refill the device with a new supply of the therapeutic substance. In order to avoid the need for surgery to access and refill the device, it is desirable to have the ability to percutaneously refill the drug reservoir. This is commonly achieved by providing the delivery device with a reservoir fill port that otherwise includes a resilient, resealable septum. The fill port is percutaneously accessible by introducing a hypodermic needle through the skin, to the fill port, and then through the septum, thereby forming a fluid connection between the needle and the drug reservoir. Implantable drug pump devices further commonly include one or more additional septum port(s), and in particular a catheter access port. The catheter access port is also accessible percutaneously via hypodermic needle, and provides direct access to the catheter, bypassing the pumping mechanism to allow the infusion of media directly into the patient, or removal of fluid from the patient (e.g., cerebral spinal fluid), via the catheter.
Although many clinicians view the catheter access port as highly desirable, others may be uncomfortable with its presence. In particular, a clinician desiring to refill the reservoir may mistakenly insert the refill needle into the catheter access port instead of the fill port. This can result in a relatively large volume of the drug being administered directly to the patient (i.e., the reservoir and pumping/metering device are bypassed and the refill volume of the drug is directly infused into the patient), potentially resulting in serious health problems for the patient. In light of this concern, efforts have been made to enhance the clinician's ability to distinguish the fill port from the catheter access port prior to, or simultaneously with, performing a percutaneous refilling procedure to better ensure that the correct port is accessed. For example, templates have been developed that facilitate the clinician's ability to visualize port locations relative to an exterior of the patient's skin. Further, screens or other needle denial devices can be placed across the catheter access port's opening; this configuration in combination with an appropriately sized refill needle can serve to prevent accidental insertion of the refill needle into the catheter access port. While fairly mechanically complex cam or rotor actuated port shields have been suggested in U.S. Pat. No. 6,805,687, such configurations may not be reliable during long-term use, and the systems described for controlling shield operation are less than optimal.
In light of the above, a need exists for improved devices, systems and methods for selectively restricting access by a needle to a catheter access port of an implantable therapeutic substance delivery device.